Structure and uncertainty: Graphical models for understanding complex data

Statistics is fundamental to making sense of the complexity of modern science. From the micro-level of the human genome to the macro-level of the universe, scientists need statistical models to help them extract meaning from empirical observations. Graphical models have been used across a wide variety of disciplines for building multivariate probabilistic models to represent, and draw inference about, complex phenomena. Nicky Best and Peter Green explain the ideas behind graphical models and show how they can be used to help tackle the challenges of complex statistical problems.     

The Effect of Gender Context on Children's Social Behavior in a Limited Resource Situation: An Observational Study

Knowing when to compete and when to cooperate to maximize opportunities for equal access to activities and materials in groups is critical to children's social and cognitive development. The present study examined the individual (gender, social competence) and contextual factors (gender context) that may determine why some children are more successful than others. One hundred and fifty‐six children (M age=6.5 years) were divided into 39 groups of four and videotaped while engaged in a task that required them to cooperate in order to view cartoons. Children within all groups were unfamiliar to one another. Groups varied in gender composition (all girls, all boys, or mixed‐sex) and social competence (high vs. low). Group composition by gender interaction effects were found. Girls were most successful at gaining viewing time in same‐sex groups, and least successful in mixed‐sex groups. Conversely, boys were least successful in same‐sex groups and most successful in mixed‐sex groups. Similar results were also found at the group level of analysis; however, the way in which the resources were distributed differed as a function of group type. Same‐sex girl groups were inequitable but efficient whereas same‐sex boy groups were more equitable than mixed groups but inefficient compared to same‐sex girl groups. Social competence did not influence children's behavior. The findings from the present study highlight the effect of gender context on cooperation and competition and the relevance of adopting an unfamiliar peer paradigm when investigating children's social behavior.     

Modelling spatially correlated data via mixtures: a Bayesian approach

Summary. The paper develops mixture models for spatially indexed data. We confine attention to the case of finite, typically irregular, patterns of points or regions with prescribed spatial relationships, and to problems where it is only the weights in the mixture that vary from one location to another. Our specific focus is on Poisson-distributed data, and applications in disease mapping. We work in a Bayesian framework, with the Poisson parameters drawn from gamma priors, and an unknown number of components. We propose two alternative models for spatially dependent weights, based on transformations of autoregressive Gaussian processes: in one (the logistic normal model), the mixture component labels are exchangeable; in the other (the grouped continuous model), they are ordered. Reversible jump Markov chain Monte Carlo algorithms for posterior inference are developed. Finally, the performances of both of these formulations are examined on synthetic data and real data on mortality from a rare disease.     

THE CORRELATES OF HEALTHY FAMILY FUNCTIONING: THE ROLE OF CONSENSUS AND CONFLICT IN THE PRACTICE OF FAMILY THERAPY

The present study explores the relative importance of individual, dyadic and triadic measures of intrafamily functioning in predicting family health. Using self-report data from 78 families, it was found that dyadic measures pertaining to marital quality and parent-child relationships were more powerful predictors than either individual measures of emotional maturity, anxiety, self-esteem or locus of control, or triadic measures of the families' hierarchical alignments. The study also found that while mothers' and fathers' assessments of intrafamily functioning were more important than the childrens' (except for the childrens' view of parent-child relationships), the parents differed in that marital quality was more important to the mothers' evaluations of the family unit while parent-child relationships were more important to the fathers'. Compositely, the findings suggest that family health is a complex multidimensional phenomenon, and that change in a particular dimension of family life may not necessarily be greeted with consensual validation or repudiation by all family members.     

Shared planning: a new foundation for quality criteria.

The Chinese word for crisis has two characters. One for danger and one for opportunity. A crisis is a time for awakening to new perspectives and for asking different questions. The widely touted "liability crisis" in the health care field provides just such a time for new approaches. Perhaps there is a way to establish market mechanisms for decision making that gives expression to the desires and values of consumers while respecting the abilities and preferences of physicians. Quality might then be the result of natural selection or, more accurately, of market demand. Such a system would acknowledge that quality in medicine is not for defining. It's for having. Quality should be obtained in bargaining for services, not in mandates of professional regulation.     

THREE APPROACHES TO FAMILY THERAPY: A STUDY OF CONVERGENCE AND DIVERGENCE*

The literature on professional development suggests that the process of segmentation or specialization within a profession logically accompanies the aggregation, dissemination and application of new and expanding bodies of knowledge. The present study empirically examines the extent and dimensions of this process of segmentation within the family therapy movement by comparing the belief and action systems of 1000 experienced family therapists oriented to one of three major models of family therapy. Two theses are suggested which may explain the findings depicting a unique patterning of similarities and differences among the three models; each implying different directives and implications for the continued growth of the interdisciplinary practice of family therapy.     

Assessing Cross-Media Impacts: A Comparative Risk Approach

The Oregon Department of Environmental Quality has developed a Cross-Media Comparative Risk Assessment model to address certain regulatory concerns. The model generates a Human and Ecological Risk Index for a facility releasing toxins into the environment. The risk indices are based on chemical fate and transport predictions, toxicity, population density, and ecological sensitive areas. The model can be used to rank facilities for inspection or as a tool to assess the progress of pollution prevention programs. Regulatory permitting departments can use the model to address the cross-media transfer of pollutants from one environmental compartment to another. The versatility of the model allows adaptation to each specific users needs.     

A Bayesian growth and yield model for slash pine plantations

We formulate a traditional growth and yield model as a Bayes model. We attempt to introduce as few new assumptions as possible. Zellner's Bayesian method of moments procedure is used, because the published model did not include any distributional assumptions. We generate predictive posterior samples for a number of stand variables using the Gibbs sampler. The means of the samples compare favorably with the predictions from the published model. In addition, our model delivers distributions of outcomes, from which it is easy to establish measures of uncertainty, such as highest posterior density regions.     

Management Information Systems and Corporate Planning

If we accept the correlation between MIS and computer based systems then the corporate planner has to consider the impact on his own company of a major new function. In so far as computers and the associated highly paid staff are concerned, the planner is certainly threatened with a major cost growth area that develops a momentum of its own. He may need all his energy to contain this growth in highly expensive resources to a scale that matches the company's overall operations. On the other hand an emphasis on management information and redesigned systems may lead to radical redesign and improvement in profitability of a company's operations. These two aspects are different sides of the same coin and in the future the corporate planner will play a dominant part in determining whether a company enjoys the benefits as well as incurs the costs of a sophisticated MIS.     

Remembering the lizard: reconstructing sexuality in the rooms of narcotics anonymous

The crack epidemic was devastating to poor American communities in part because of the destruction wrought by the system of exchanging sex for drugs, which was a key feature of the crack-use culture. Sex-for-drugs exchanges were often conducted under unsafe circumstances and were linked to the spread of AIDS and other STDs, as well as unplanned pregnancies. The existence of this alternative system of sexual relationships threatened the economic viability of established commercial sex work and undermined the status and power of women. Narcotics Anonymous (NA) meetings helped men and women recover from crack addiction through a well-described 12-step process. Described as the rooms, these time- and space-specific encounters helped people become sober in the context of neighborhoods that were centers of the drug trade. Because of the key role of sex in the crack culture, transformation of sexual relationships was essential to establishing and maintaining sobriety. The manner in which the rooms of NA influence the sexuality and lifeworld of addicted people is explored using Barker's theory of ecological psychology.